1. Field of the Invention
The present invention relates to a lens driver capable of moving a lens by using an electromagnetic force produced by a coil, a magnet, and a yoke, a camera module, an imaging apparatus, and a camera-equipped mobile terminal, and particularly to a technology that readily allows size reduction and efficient lens motion.
2. Description of the Related Art
In recent years, a variety of camera-related apparatus have been popular, for example, imaging apparatus, such as digital still cameras and video camcorders, and camera-equipped mobile terminals, such as mobile phones, PDAs (Personal Digital Assistants), and notebook personal computers into which a camera module is incorporated. Among these apparatus, an apparatus with an autofocus function and a zoom function has lens drivers incorporated therein to move the entire optical system formed of a plurality of lenses, a single lens or a group of lenses for focusing, and a single lens or a group of lenses for zooming in the optical axis direction.
In a lens driver used for the purposes described above, a linear motor is used to move a lens in the optical axis direction. A linear motor is advantageous in that the magnetic flux focuses well and the magnetic flux flowing through a yoke tends to be uniform. Among a variety of linear motors, a voice-coil linear motor, which is advantageous for space saving, is commercially used in an imaging apparatus having an autofocus function and a zoom function and other apparatus.
In a linear motor-based lens driver using a known technology, a lens holder holds a lens unit and a guide shaft supports the lens holder movably in the optical axis direction. In this technology, a linear motor formed of a coil, a magnet, and a yoke moves the lens holder in the optical axis direction, and a magnetic member holds the positioned lens holder (see JP-A-2008-40077, for example).